help with a diff code?

[fuzzy]

the code on the tag attached to the back of my spare diff reads 1140A4641S. can anyone shed some light as to which numbers relate to the ratio?
thanks.

[EThreezero]

4.64? fook knows geez

[mrLEE30]

it means 40 ring teeth divided by 11 pinion teeth making the ratio 4:1, A means it is a replacement final drive, and it is not a LSD.

see i can be fun!!

mrlee

[fuzzy]

when you turn the prop flange should the 2 driveshaft flanges on an lsd turn the same way or opposite directions?

[craigieeb]

L.S.D turns the same way fella

[mrLEE30]

sorry my mistake didn't read your diff code correctly!!

it is an LSD due to the ''S'' at the end of the code (and it is a replacement diff by BMW due to the A)!! and yes they should both turn same direction unless the diff clutch is knackered.

and the ratio is 4:1

sorry

[fuzzy]

thanks for the info,i wouldnt call that fun but its certainly informative
how would that diff alter the performance over the original 3.91 diff.would that be higher top end but slower acceleration or would the difference be hardly noticable?

[mrLEE30]

yep you would gain more top end speed (but unlikely as aerodynamic drag on a 20+year old design really limits top speed) and you would loose a bit of acceleration about 2-3%, so i doubt you would really notice much change.

however on a plus note you may gain the 2-3% back on fuel economy on a long distance run, which is about the cost you save by running with no lights on and not using the windscreen wipers and stereo!! you could save 5-6% or 5p in every pound!! now that is fun!! (assuming you stick to the speed limit like me )

mrlee

[fuzzy]

well thats that idea blown out as youve probably guessed by now i sometimes speed so fuel economy is at the bottom of my list of priorities.if the difference is that small in performance i might as well keep the original 3.91 fitted and sell this 4.1

[Jon_Bmw]

Erm not sure if i have read MR lees advice right there or not.

the 4.1 ratio WILL give you faster acceleration but less top speed

the 3.91 ratio will give less acceleration but more top speed.

[Andy335Touring]

What sort of maximum speeds are you getting out of each gear ?

Some times going too short geared can actually slow your over all acceleration down due to to many gear changes and not making best use of the available torque/power.

Short gearing is good for in gear acceleration though, especially higher gears like 4th and 5th.

[StuBeeDoo]

it means 40 ring teeth divided by 11 pinion teeth making the ratio 4:1,

Surely 40 divided by 11 is 3.63636363 making the diff in question a 3.64??

[fuzzy]

that would explain the roughly 3.7 turns of the driveshaft flanges to 1 turn of the prop flange. :?as for top speed it runs out of steam at about 120-125 mph on the 3.91 diff. acceleration is my priority rather than top end, first gear is almost useless and as im using the correct cosworth T5 gearbox it must be down to the diff ratios.

[StuBeeDoo]

How would that diff alter the performance over the original 3.91 diff.would that be higher top end but slower acceleration or would the difference be hardly noticable?

OK, so I don't have the power you do, but when I took the standard 4.27 out of my Touring and put in a 3.64, my "arse-dyno" didn't notice any difference. It will pull over 60 in second now though, so the 0-60 time may be fractionally quicker due to not having to change into 3rd at 55.

[320Touring]

How would that diff alter the performance over the original 3.91 diff.would that be higher top end but slower acceleration or would the difference be hardly noticable?

OK, so I don't have the power you do, but when I took the standard 4.27 out of my Touring and put in a 3.64, my "arse-dyno" didn't notice any difference. It will pull over 60 in second now though, so the 0-60 time may be fractionally quicker due to not having to change into 3rd at 55.

glad to hear that dude-thinking of going 3.64 myself..

Fuzzy, fitting 3.64 to my 4.27 touring would mean about a 600-700 rpm drop in engine speed at a given road speed in 5th

eg 4.27 gives 80mph @4000rpm

3.64 gives 80mph @3300ish rpm

therefopre the car is higher geared. would sort out your "short first" issue but may make top end a bit longer (relatively!!!)

[StuBeeDoo]

How would that diff alter the performance over the original 3.91 diff.would that be higher top end but slower acceleration or would the difference be hardly noticable?

OK, so I don't have the power you do, but when I took the standard 4.27 out of my Touring and put in a 3.64, my "arse-dyno" didn't notice any difference. It will pull over 60 in second now though, so the 0-60 time may be fractionally quicker due to not having to change into 3rd at 55.

glad to hear that dude-thinking of going 3.64 myself..

Fuzzy, fitting 3.64 to my 4.27 touring would mean about a 600-700 rpm drop in engine speed at a given road speed in 5th

eg 4.27 gives 80mph @4000rpm

3.64 gives 80mph @3300ish rpm

therefopre the car is higher geared. would sort out your "short first" issue but may make top end a bit longer (relatively!!!)

Neil, Hi Dude, how's things?
You won't regret putting in a 3.64. TBH, it hasn't made much difference to my fuel consumption, but it's far more "relaxed" to drive at speed.
The difference between the 4.27 and 3.64 makes 4th (3.64) almost exactly what 5th (4.27) was (if you see what I mean).
Put another way, 5th is now more overdrive, rather than just "top".
It doesn't affect 1st very much, because it's so short to start with. I think the only way to sort that issue would be to put a Sport 'box in.

[320Touring]

glad to hear that dude-thinking of going 3.64 myself..

Fuzzy, fitting 3.64 to my 4.27 touring would mean about a 600-700 rpm drop in engine speed at a given road speed in 5th

eg 4.27 gives 80mph @4000rpm

3.64 gives 80mph @3300ish rpm

therefopre the car is higher geared. would sort out your "short first" issue but may make top end a bit longer (relatively!!!)

Neil, Hi Dude, how's things?
You won't regret putting in a 3.64. TBH, it hasn't made much difference to my fuel consumption, but it's far more "relaxed" to drive at speed.
The difference between the 4.27 and 3.64 makes 4th (3.64) almost exactly what 5th (4.27) was (if you see what I mean).
Put another way, 5th is now more overdrive, rather than just "top".
It doesn't affect 1st very much, because it's so short to start with. I think the only way to sort that issue would be to put a Sport 'box in.[/quote]

hi stuart the touring is sweet as dear fellow:-)

Like the sound of 4th seeming like 5th-hammoj28 will tell you the m20b20 pulls lovely from 1k in 5th

how goes your touring? i've got several big plans for mine in the offing

with regards to the box-fuzzy is using the t5 box to go with the cozzy lump, so I dont know the exact ratio's, however I do know that the 320i had gear ratios (1st 2nd 3rd) that are almost identical to a sport box

[StuBeeDoo]

hi stuart the touring is sweet as dear fellow:-)

Like the sound of 4th seeming like 5th-hammoj28 will tell you the m20b20 pulls lovely from 1k in 5th

how goes your touring? i've got several big plans for mine in the offing

with regards to the box-fuzzy is using the t5 box to go with the cozzy lump, so I dont know the exact ratio's, however I do know that the 320i had gear ratios (1st 2nd 3rd) that are almost identical to a sport box

Sorry Neil, gotta shoot you down there! Agreed 2nd & 3rd are very close matches, but 320i 1st is 3.72, Sport 1st is quite a bit longer - 3.38.

I know about the pulling from 1k in 5th. Before I swapped diffs, I only ever used 2nd 3rd 4th and 5th!.

I'll PM you, 'cos I don't want to go off topic here.

[320Touring]

Sorry Neil, gotta shoot you down there! Agreed 2nd & 3rd are very close matches, but 320i 1st is 3.72, Sport 1st is quite a bit longer - 3.38.

I know about the pulling from 1k in 5th. Before I swapped diffs, I only ever used 2nd 3rd 4th and 5th!.

I'll PM you, 'cos I don't want to go off topic here.

oh ok i still win as 2 out of 3 aint bad

just to reiterate fuzzy, 3.64 good for top end, 3.91 for eyebulging acceleration

[fuzzy]

thanks for the info guys,bottom line is ill stick with the 3.91 im using at the moment

[Andy335Touring]

What sort of maximum speeds are you getting out of each gear ?

Some times going too short geared can actually slow your over all acceleration down due to to many gear changes and not making best use of the available torque/power.

Short gearing is good for in gear acceleration though, especially higher gears like 4th and 5th.

[mrLEE30]

woops, got my maths and my ratios wrong way round!!

i'll get my coat!



mrlee

[Jon_Bmw]

woops, got my maths and my ratios wrong way round!!

i'll get my coat!



mrlee

No worries chap, I couldn't work out whether you were refering to the old diff or the new diff. Anyway all sorted now